1. Field of the Invention
The present invention relates to a substrate processing method, a substrate processing apparatus, and a manufacturing method of a semiconductor device. In particular, the present invention relates to a substrate processing method and a substrate processing apparatus for use in a liquid immersion exposure process, and a manufacturing method of a semiconductor device with using the method and the apparatus.
2. Description of the Related Art
Recently, attention has been focused on an exposure method referred to as a liquid immersion exposure method. The liquid immersion exposure method is provided as an exposure method for carrying out patterning on a resist film while a gap between a projection optical system (projection lens) of an exposure apparatus and a processing target substrate (exposure target substrate) to be applied with exposure treatment is filled with a liquid (immersion liquid) having a high refractive index. The gap between the projection optical system and the resist film is filled with an immersion liquid, whereby a deeper focal point can be obtained. Currently, pure water is generally used as an immersion liquid. A technique relating to liquid immersion exposure is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-303114. However, if pure water exists in a resist film shape, there is a danger that a photoacid generator agent or the like is eluted from the inside of the resist film into the pure water. If the photoacid generator agent is eluted from the inside of the resist film into the pure water, it becomes difficult to properly pattern the resist film. In order to avoid such a problem, there is proposed a technique of further providing a cover film on the resist film.
In a general exposure target substrate (wafer), its peripheral rim part is formed in an inclined shape such that the thickness becomes smaller as it goes from a radial inside to a radial outside of the wafer. Of the peripheral rim part of the wafer, a portion having an inclination is referred to as a bevel portion. Of course, the pure water on the wafer is likely to leak from the bevel portion to the outside of the wafer. If the pure water leaks out from the top of the wafer, it becomes difficult to properly carry out liquid immersion exposure. Therefore, in order to prevent the pure water from leaking out from the bevel portion at the time of liquid immersion exposure, it is desirable to cover a region from a center part of the wafer up to the outer face of the peripheral rim part with the cover film.
However, in a general liquid immersion type exposure apparatus, a slight gap always exists between a wafer and a wafer stage on which the wafer is placed. For this reason, it is very difficult to completely restrict liquid leakage from the bevel portion. In addition, there is a high danger that the liquid leakage from the bevel portion causes a problem that pure water goes around the back face side of the wafer. In a state in which the pure water goes around the back face side of the wafer and the back face side remains wet, which leads contamination of the wafer stage of the exposure apparatus and quality deterioration of wafers to be processed later. Finally, in a semiconductor device manufactured by using such a wafer whose quality deteriorates, there is a high danger that its performance, quality, reliability or the like deteriorates.